Or a much easier way is to set up NOOBS and select Raspbian. When you do the configuration select it to always boot to a desktop. Once it is set up, reboot and when it comes up to a desktop click on the "start" icon in either the lower left or upper left corner (depending on how you have your menu bar set). Go to WiFi configuration. I think V1.3 of Raspbian put an icon on the desktop. V1.4 doesn't seem too. Scan all the available networks. Select yours and put in your security key. Click on Connect. You are done.